A feed chain of the aforementioned type is known. When a short-circuit appears inside or outside the electric machine, an overvoltage or overcurrent of the feed current is detected. If the short-circuit is outside the electric machine, one commonly adopted solution consists of using the control means to command the opening of the switches of the insulating device. This solution makes it possible to insulate the electric machine from the feed chain and thereby protect it from the overvoltage or overcurrent that has been detected.
However, if the short-circuit is inside the electric machine, significant pulsed torques as well as short-circuit currents are created within the electric machine. Opening the insulating device is then not enough to reduce the amplitude of those pulsed torques and currents sufficiently. The electric machine is in fact driven by the wheels of the train in which it is installed, thereby operating in “alternator” mode. The pulsed torques as well as the short-circuit currents created then risk leading to unwanted phenomena, for example such as an axle locking.